Statistical analysis of ice-induced loads on the norstromsgrund lighthouse

Abstract

Structures may experience ice-induced vibrations under a wide range of ice conditions. This paper presents a statistical analysis of ice-induced forces on the Norströmsgrund lighthouse. A total of 61 measured events of ice-induced frequency lock-in (FLI) vibrations from 2001 until 2003 are considered. For each event, a smoothing algorithm for joint input-state (JIS) estimation is used to identify the time series of ice-induced dynamic forces based on measured accelerations. The smoothing algorithm is validated by comparing the identified dynamic force with the measured dynamic force. Statistical analysis on these 61 events indicates that the identified force directions agree well with the observed ice-drift directions. However, a universal relation between peak force and ice thickness or ice velocity is not found. Significant peak forces are likely to occur under ice conditions with ice thickness between 0.65m and 0.85m and ice velocity ranging from 0.042m/s and 0.05m/s.